A power supply controller having the following configuration is known. In a power-supply path that connects a load to a power source, a high-power semiconductor switch such as a power MOSFET is provide to control an amount of current to the load by turning on and off the semiconductor switch. With this configuration, the power-supply path to the load is protected against an overcurrent. When an excessive current flows in such a power supply controller, a potential at a control terminal of the semiconductor switch is adjusted by a control circuit. Namely, the semiconductor switch is turned off and the current is shut off (see Patent Document 1).
If the power supply controller is used as a power supply controller for a vehicle, it is set to a power saving mode (sleep mode) when no instruction for driving the load is issued so that a battery can be kept from running out. In the sleep mode, functions of the power supply controller are usually halted except for a sleep-mode cancellation function.    Patent Document 1: Japanese Unexamined Patent Publication.